This week we will celebrate fossil sharks of the Mesozoic that have been found in Arkansas. Because all of our surface rocks of the period are from the Cretaceous, the sharks are limited to that time. There are other cool sharks from the Paleozoic, but they will have to wait for another time. Hunting for shark teeth in Arkansas can best be done in the chalk formations called the Annona and Saratoga in southwest Arkansas. But you can also find them in several other formations as well.
Many of the sharks found in the Cretaceous in Arkansas have contemporary species. While the species may vary, the genus name is very long-lived. For those who are unaware, scientific names follow a binomial system, with a genus and a species name, the genus being the first name and indicating a group of very closely related species. It is next to impossible to tell the difference between species of sharks just by their teeth unless, and many times even if, one is an expert, so I will be sticking with the genus names.
To begin the week, I present to you Ginglymostoma, the nurse shark.
The scientific name comes from the shape of its mouth. The origin of the name nurse shark is not clear, but it is considered likely to have originated with the Old English word Hurse, for sea floor shark.
Known for its puckered mouth and barbels on the sides of its mouth, nurse sharks spend most of their time near the sea floor scrounging for whatever small animal they can catch. They are very docile and will only bite if provoked. Humans are far too big for nurse sharks to be interested in, so unless one really goes out of their way to annoy a nurse shark, you’re pretty safe, even from the largest ones, which can get over 4 meters.
We have reached the end of Paleo-Animal Fest celebrating the animals that populated the Cretaceous seas of Arkansas 65-120 million years ago. We have seen early crocodilians and gars. We have seen the largest of the predators in the ocean and some of the smallest of creatures populating the seas. Today we are going to wrap it up with an animal famous the world over: elasmosaurs.
Many people today will not know them by that name, but show them a picture of Nessie, the Loch-Ness Monster, and the image they conjure up is the classic elasmosaur, a long-necked marine (which is funny because Loch Ness is a freshwater lake) reptile with big flippers and a small head, essentially looking like a predatory aquatic sauropod. Of course, it probably didn’t hold its head way out of the water like shown in most imaginings, but the general appearance is close.People are frequently pulling things out of the ocean and claiming they are long-lost Mesozoic Monsters from the time of the dinosaurs. Of course, they always wind up being something else.
Sadly, elasmosaurs died out the same time the big dinosaurs died out.But they had a good run, first appearing in the Triassic, close to the beginning of the Mesozoic Era. Elasmosaurs were part of a group called sauropterygians, which first appeared over 200 million years ago.
Here are a couple of illustrations of elasmosaurs. One is by my son, which will be appearing in a booklet I am making about Arkansas during the Cretaceous, as well as a coloring book for kids I am putting together. Some of them really did have amazingly flexible, ridiculously long necks.
Here is one in the expected habitat and following expected behaviors.
Come back next week to celebrate Arkansas Cretaceous Shark Week.
Welcome to Day 4 of Paleo-Animal Fest, celebrating the creatures populating the Arkansas seas during the Cretaceous. Today we are going to look at a fish that has survived for an amazingly long time. They first appeared in the Late Cretaceous and have survived to the present day, still thriving. You can find them in many freshwater lakes and rivers, especially brackish and hypoxic (low oxygen) waters, even into marine waters on the occasion. They are a tough predator in many ways, from their durability in the fossil record to their physical defenses and their intimidating jaws. I am of course talking about gars.
Gars are piscivorous, meaning they eat other fish. The most common description of them is “voracious predator.” They are known for their tooth-filled jaws, scales of armor, and their fight. Their typical mode of attack is a lightning-quick sideways bite. Gar fishermen are often called “not right in the head.”
Gars can be found in many places within North America, but their fossils can be found all over the world. The vast majority of the fossils have been identified as Lepisosteus, which includes the longnose, shortnose, spotted, and Florida gar. However, most of their fossils are isolated scales, which makes it difficult to impossible to tell what type of gar it is from. So I am going to go with most people’s favorite gar, Atractosteus spatula, the alligator gar (pictured above). It is the biggest one reaching almost 3 meters. Another impressive armored, ancient fish that is still around is the sturgeon, which can get a lot bigger, but are nowhere near as impressive in the teeth department.
There are not a lot of skeletons of gars with heads and tails, but there are a lot of body pieces covered in scales. Gar scales are thick, rhomboid-shaped ganoid scales, meaning they are covered in what is effectively enamel. The scales form an excellent armor, making handling them hard on the hands. They are so tough and dense, in fact, that the scales have been used as arrowheads and make even CT scans on gars hard to impossible to get decent views. On the plus side, this results in them having excellent preservational potential and can be found quite commonly. The scales make the fossils really stand out and readily identifiable to at least the group Lepisosteiformes.
By far, the most complete and detailed description of gars ever published is by Lance Grande, the universally acknowledged leading world expert on fossil fish, called “An empirical synthetic pattern study of gars (Lepisosteiformes) and closely related species, based mostly on skeletal anatomy. The resurrection of Holostei.” Special publication 6 of the American Society of Ichthyologists and Herpetologists, published in 2010. This is a massive tome, amassing almost 900 pages of detailed observation on gars. This book is a companion to a similar volume he did on bowfins. I can honestly say I have never seen a more thorough job on any group such as this in my life. Every time I look at it, I think wow, all this on just gars? This would make any scientist proud to have one of these capping their life’s work and this doesn’t even begin to touch the work put out by Grande. I am in awe.
Monday was a goniopholid crocodilian. Tuesday was mosasaurs, the largest of the marine predators. For day 3, we’re going to the other end of the scale.
What is a picture of a rock outcrop doing here? This is a picture of the Saratoga Chalk, courtesy of the Arkansas Geological Survey. Look at it this way, and it is tons of chalk, the same that they used to make for blackboards when they used the real thing.
But look at it under a microscope and you open up an entirely new world. For chalk is not just a rock. It is a rock made of trillions of shells of microscopic organisms that live in the oceans.
Two kinds of microorganisms make up most of the chalk. The Saratoga is primarily noted for its abundance of foraminifera, (forams for short) one-celled organisms that form shells, or tests, out of minerals dissolved in the sea water. The ones that make up chalk and limestone form theirs out of calcium carbonate. It is unclear what they are related to, but one thing is clear. They have developed a huge diversity in their over 500 million years of existence.
I find forams fascinating because of their wonderful diversity. Here is another picture posted on the blog “Letters from Gondwana.” The article is a nice description of forams if you want more information on them.
The other group that is commonly found in chalk is called the coccolithophores. These are very tiny, once-celled plants found in the ocean and make up one of the largest groups of phytoplankton. They also make shells of calcium carbonate, but instead of a shell like the forams, they create their home with a few dozen intricately formed scales.
The coccolithophore Gephyrocapsa oceanica. Wikipedia.
When the cells die, the scales scatter and become tiny grains of calcium carbonate which, when piled up on the ocean floor with all the other debris from the oceans, can form those particles of chalk that you used to clean off the blackboard.
Both of these groups prefer shallow, warm seas. Go to the Bahamas or the Persian Gulf and you will get an idea of the environments that are admirably suited to making modern day chalk, as well as getting a good idea of what Arkansas was like 100 million years ago.
Continuing our celebration of marine animals of the Cretaceous found in Arkansas, here is a picture of a mosasaur. It is from the Dallas (Perot) Museum of Nature and Science. They have a great display of several different mosasaurs. You can also see one on display at the natural history museum located at the University of Texas at Austin.
Mosasaurs were the apex predators of their time, which was in the Late Cretaceous. Tyrannosaurs may have ruled the land, but mosasaurs ruled the seas. The first mosasaurs appeared in the early Cretaceous, but by the end, they dominated the oceans. Unfortunately for them, they only had a 20 million year or so run at the top before the mass extinction at the end of the Mesozoic Era wiped them out along with the dinosaurs.
Mosasaurs were not related to dinosaurs, other than also being reptiles. They were most closely related to the group of lizards that include the monitor lizards, such as the Nile monitor and Komodo Dragon. They were fast predators with a powerful tail to move them through the water. Mosasaurs were so adapted to the water that they bore live young and were not able to walk on land, although they did still have to surface for air like every other reptile. Recent research has found they were endothermic (warm-blooded), unlike their competitors, giving them an edge by allowing them to sustain higher activity levels. It also meant they had to eat more often, making it necessary for them to be effective hunters. Research has also indicated they were countershaded, with a lighter belly than the back, much like many sharks of today. They had a varied diet, with some species specializing in different prey, so over the whole group, they pretty much ate everything in the ocean.
Mosasaur bones have been found in many places throughout southwest Arkansas, which was covered by the Western Interior Sea during the Cretaceous. Two species have thus far been recognized. Platecarpus was fairly small, only 4-5 meters (13-16 feet), but were noted for some exceptionally preserved fossils that retained the impressions of a tail fluke, allowing paleontologists for the first time to see what their tails looked like. The other species is Mosasaurus itself, a huge predator that reached lengths of 15-18 meters (50-60 feet).
Welcome back to the new school year. Some of you will be excited to be back, seeing old friends, making new ones, and learning new things. Some of you will be sad to see summer end. Many of you will be doing both at once. Others of you of course aren’t in school and don’t care about it, but if you are here, you are nevertheless interested in learning cool new stuff. So it is a time for a celebration of the natural world.
Shark Week is a big summer event on the Discover Channel. It is probably their biggest viewer draw all year. Who doesn’t like learning about sharks and seeing them in all their awe-inspiring glory? Additionally, if one is keeping up with the weather, southern Louisiana is currently being deluged, with Baton Rouge and surrounding areas practically getting washed away.
So I thought this would be a good time for Paleoaerie to hold its own version of Shark Week. I can’t do a series of tv specials, so I am going to extend my Paleo Shark week over two full weeks. All this week I will be putting up short posts on marine creatures that swam in the oceans of southern Arkansas during the Cretaceous. Every day will be a new post on something that would make your swim…interesting. Next week will truly be Paleo Shark Week. Every day next week will be highlighting a different shark that would be swimming in the Cretaceous waters of southern Arkansas.
To kick things off, I will start with this creature.
This is a crocodylomorph, meaning that it is in the same group that includes crocodiles and alligators. Specifically, it is a member of the family Goniopholididae. Species in this group were, at least superficially, similar to modern crocodilians. They were semi-aquatic hunters living in marsh and swamp lands. They wouldn’t look out of place with the modern alligators swimming around Arkansas today, except that they probably couldn’t compete effectively with alligators, who are better adapted for the lifestyle than they were. They lived throughout much of the Mesozoic, from the early Jurassic to the Late Cretaceous, when the more modern forms replaced them.
Goniopholids are what is known as mesosuchians, which means “middle crocodiles”. Mesosuchians, as the name suggests, were more derived than the earliest crocodyliforms, such as the protosuchians, although less derived than modern-day crocodilians. Mesosuchians is not a formal name, but an informal and decidedly paraphyletic (i.e. not a valid cladistic grouping because it leaves out some descendants) name to designate those crocodyliform species showing the early characteristics and those that show the characteristics of the modern crocodilians. Here is a phylogenetic tree put out by Chris Brochu in 2001, showing the general relationships within the crocodylomorphs. The names on the left side of the long main line include everything from that point on, e.g. Crocodymorpha includes “sphenosuchians” and everything below it, but not the Aetosauria and above. Mesosuchians plus Eusuchia (which does include all modern groups) can correctly be called Mesoeucrocodylia, but that hardly helps us specify the group.
Mesosuchians include a wide variety of animals with a large number of species. They include terrestrial animals like the carnivorous boar croc Kaprosuchus and the herbivorous Simosuchus, as well as the more typical semi-aquatic pholidosaurs, which include the super croc Sarcosuchus, one of the largest crocodylomorphs ever, reaching almost 40 feet.
Sarcosuchus may not have been quite as big as Deinosuchus though. Deinosuchus was an alligatoroid (within the larger alligator family, but not a modern alligator), which potentially reached upwards of 40 feet, but may have been heavier set. Sarcosuchus lived in the early Cretaceous at the same time as Goniopholis in Arkansas, but lived in Africa and South America. Deinosuchus, on the other hand, lived int he Late Cretaceous right here in Arkansas. While we have no bones to prove this, we do know they lived in Texas and Mississippi, as well as many other places in the United States. The environment would have been suitable for them, so there is no reason to think they did not live here as well.
One question I get asked a lot when I show fossils to people is “Is it real or fake?” It is a question that always irks me because it seems very few people understand that this is an entirely wrong question.
People like to categorize things into binary bins. Is it black or white? Republican or Democrat? Is it raining or not? Do you accept science or religion? Of course, none of these questions make any sense as an either/or question. Just like real or fake, all of these questions miss the fact that there is more to it than one or the other. All of them can only be correctly answered if one is cognizant of the other variations. So today, I am going to introduce to you a more nuanced view of whether or not the fossils you see in museums are real or not.
Real fossils need little explanation. They are the actual fossil material. Whether or not it is actual bone or shell being preserved, a bone that has been replaced with minerals, a natural mold, or other some such style of preservation, they are real.
Real in this case does not mean it is remains of the actual organism, although it can be. Bone, shell, leaves, and other tissues can be preserved indefinitely under the right conditions. Usually however, they are replaced with minerals or remain only as impressions in the sediment. In any case, these are all real fossils. They are the original fossil found, dug up, and brought back to the institution or person to whom it belongs.
Replicas are casts or molds made from the actual fossil. They are made to look as close as possible to the original fossil. These are made so that the original can be protected while the copy is shown to many more people than could see the original. Use of replicas allows copies to be put in the hands of many people all over the world. In many instances, the original is too fragile or heavy to safely transport.
The important point about replicas is that they are not fakes. They are duplicates of a real fossil. In some cases, they can be even better than the real thing. After decades of handling, the original fossils can get worn or broken, with details once present no longer visible.
Fakes, on the other hand, represent something that is not only not real, but never existed. Many fakes are designed to deceive and so are often called forgeries. The difference between what many people think of as forgeries and what we are talking about here is that forgeries are usually designed to trick people into thinking they are the real thing. A replica, if presented as the real thing, would be considered a forgery. However, in paleontology, most things described as forgeries are in reality fakes designed to deceive people into thinking a fiction is real. Fakes are never acceptable in museums unless explicitly labeled to indicate that they are fantasies. The Piltdown Man is an example of a fake. It was made with the express purpose of making people think it was real, when in fact it was created from bits of human and animal bones that were altered to make them look like they belonged to the same primitive human.
Archaeoraptor was another fake. This one adds a wrinkle in the topic though. Archaeoraptor was made by gluing pieces of different fossils together. The individual pieces were real, but the resulting chimera was a fake.
As Archaeoraptor shows, fakes don’t have to be unreal to be fictional. There are lots of fakes that are real fossils put together in intentionally misleading ways. In the case of Archaeoraptor, they were simply trying to make the fossils more spectacular so they could sell them for a higher price. Others are done to discredit scientists or simply as pranks for fun.
Of course, there are plenty of fakes that are made up out of whole cloth. Numerous “human” footprints found with dinosaur tracks are nothing more than carvings designed to trick gullible people. I have personally seen several in which the tool markings were clearly visible. The most famous picture of the Loch Ness Monster, known as the surgeon’s photo, was a fake.
So remember, when you are going to a museum or looking at fossils from a paleontologist, you may be looking at real fossils or replicas. But you will never be looking at fakes. They may not be the original fossils, but they are not trying to mislead you or lie to you, which is what fakes are trying to do. If you really want to see fakes, try here or here. And please, don’t insult your local paleontologist by saying they are showing you fakes when all they are doing is showing you replicas of real fossils that you might otherwise never be able to see.
I know it has been forever and a day since I last posted, but I have not disappeared and Paleoaerie is not going away. I have been busy and pondering a reorganization for the website. One of the things that has kept me busy is a series of talks that I have given and, most importantly, am about to give. Mid-America Science Museum has asked me to be the guest speaker for their dinosaur exhibit over the summer. I will be giving one set this Saturday, July 23 and again on Saturday, September 3.
It is my plan to put all these talks online. But one thing I have learned this summer is that I am truly horrible at making a video that requires me to actually talk in it. So I am trying to figure out a way to get over that problem and bring my talks to you. In the meantime, here is a short description of the talks.
New Discoveries in Paleontology: This talk will focus on, as the name suggests, new discoveries in paleontology. I will be discussing new dinosaurs that have been found this year, but the majority of the talk is discussing how paleontology has gone high tech and what we have found with these new techniques.
Tyrannosaurs vs. Spinosaurs: A question that gets asked of all palentologists since Jurassic Park III came out is who would win in a fight between T. rex and Spinosaurus. So this talk discusses the new science on tyrannosaurs and comparing them with what we know of spinosaurs.
Mesozoic Arkansas: This talk covers what Arkansas was like during the Mesozoic, including all the different fossils that have been found in the area.
Dinosaurs, Giant Sharks, and Evolution: Selected Good (and Bad) Educational References: This is a talk I gave in April at AAIMS, the Arkansas Association of Instructional Media Specialists. I cover good books, websites, and shows on these topics, as well as a few to avoid.
500 Million Years of Natural History: Arkansas’s Secret Treasures: Here I give a brief rundown on all the fossils of Arkansas, starting from the Cambrian all the way up to the Ice Ages in the Pleistocene.
If you have a particular talk you want to see, let me know and I will concentrate on getting that one as soon as I can. If you can make it to Hot Springs, AR this Saturday or in September, stop by the Mid-America Museum and hear these talks in person.
No one hazarded a guess on the puzzle posted last week. It’s an interesting animal I found most curious. Here is the puzzle again.
The animal this refers to is often referred to as a bearcat or occasionally bearweasel, although it is neither a bear, nor a cat, nor a weasel. Of the three, it is most closely related to the cats. What I am talking about is the binturong, aka Arctictis binturong.
Binturongs live in the tropical rain forests of southeast Asia and are viverids, along with civets, linsangs, and genets. If you’re like most people, you may have a vague recollection of what a civet might be and no idea at all what linsangs and genets are. Fortunately, Toni Llobet has very helpfully illustrated them for the Handbook of the Mammals of the World, Vo1. 1: Carnivora, in 2009. He’s done a huge number of excellent illustrations for that text. If you are at all interested in mammal diversity, it is worth checking out.
Binturongs look tough and surly, with bushy black or brown fur with whitish or rust-colored highlights giving them a grumpy old man kind of look. They are in the Order Carnivora, so that would seem to fit, but in reality they tend to spend their days sleeping and their nights ambling around the trees looking for fruit. While fruit is their favorite, they aren’t too picky, and will pretty much anything they come across that doesn’t run away fast enough, which doesn’t have to be that fast because the binturong isn’t going to bother chasing down a meal when pretty much everything qualifies as a potential meal.
Many mammals use scent to mark their territory and to advertise and often have particular glands to make oils that carry the scent. Binturongs have an unusually distinctive smell. It is said they smell like buttered popcorn. The San Diego Zoo has a nice web page about them (which served as the main reference for the last two paragraphs) if you want to read more about them.
I said earlier that Binturongs are often referred to as bearcats, and occasionally as bear weasels. This is one of the things I find interesting about them because, other than all of them being in the Order Carnivora, none of those four are related. There is some debate as to the precise relationships within the carnivorans, but all the hypotheses put these animals in separate clades, or groups.
Before I get into this, there are a couple of things I want to clarify for the non-phylogenetically trained readers. A species can also be called by a more general term called a taxon. A taxon (plural taxa) is simply a species or group of related species. Mammalia is a taxon that contains all the mammalian taxa. If a researcher uses a method called cladistics, which almost everyone these days does, every taxon above species can also be called a clade. This was done to get rid of trying to come up with names for all the different ranks. When you got really detailed, it got kind of ridiculous having Sub-infra-super-supra-mega-gigantor-gonzo-teenytiny…attached onto everything. The number of prefixes could get absurd. It also gave people the false sense that things like Families or Orders actually meant comparable things when in reality they meant nothing at all, yet people still insisted on comparing them as if they meant the same things. A family of insects has little evolutionary similarity with a family within mammals and should not be compared. Taking away ridiculous names lessened (but sadly did not stop) the proclivities of people to do silly things like that. All these relationships can be mapped onto what is called cladograms or phylogenetic “trees”.
Now that everyone understands all that, it is important to understand that when scientists talk about carnivores and carnivorans, they are talking about two entirely different things, which, I know, is stupidly confusing and the scientists who are responsible for this should be slapped soundly and I humbly apologize. Carnivores refers to animals that eat meat as their primary diet. It has nothing to do with their relationships to one another and this is the way most people think about the term carnivores. Wolves are carnivores, just as are sharks, even though one would have to go very, very, very far back to find a common ancestor. Carnivorans, on the other hand, are those animals within the the Clade Carnivora. These animals include all animals more closely related to cats and dogs than anything else, including hyaenas, bears, seals, pandas, weasels, raccoons, skunks, and many other animals, including viverids. Carnivora is based on relationships, not diet. Thus, not all carnivorans are carnivores.
Now that I have gone through all that, binturongs are omnivorous, not carnivorous, carnivorans. As I stated earlier, they belong to the clade Viverridae. How do they relate to bears (Ursidae), cats (Felidae), or weasels (Mustelidae)? It is a bit of a debate, but they are closer to cats than the others. The first thing to know is that clade Carnivora is generally split into two major groups: Feliformia, the cat-like animals, and Caniformia, the dog-like animals. Here is a supertree published in 2012. A supertree is basically a compilation showing the consensus of a whole bunch of published trees of different parts. Each species that is added to the list increases the number of possible relationships exponentially, so trying to make a tree that shows all the species of carnivorans gets mathematically hideously complex. So people study their favorite group within Carnivora and then a supertree is put together with all of them together.
Nyatura and Bininda-Emonds chose to make their tree in a circular format, which is popular for including a large number of species, but is unfortunately the most difficult format for people to understand. It works just the same as all the other trees, it is just bent around and following the lines connecting the groups may be difficult for some.
At any rate, all the clades making up Caniformia are above the dotted line, which I added to hopefully make this easier to read, and all the clades in Feliformia are below the line. Viverrids, including our friend the biturong, is in purple at the bottom, most closely associated with groups like the Hyaenidae (hyaenas), Herpestids and Eupleridae (mongoose, fossa, and meerkats), and then of course, less closely, the felids. The bears and weasels are both in Caniformia and quite far removed from the biturong.
Here is another view of the data in a much simpler format to understand, published by Blaire Van Valkenburgh et al. in 2014.
Other phylogenies may differ slightly by placing the viverrids a bit closer to the prionodontids and felids than hyaenids, but most everyone agrees that is the general area they belong. From this it is quite clear that viverrids are their own thing and only superficially resemble any of the animals they are often referred to as, but evolutionarily, they share a much closer common ancestor with cats than they do with either bears of weasels. So they aren’t bear-like cats, or cat-like bears, or weasel-like, bear-like cats. We humans just like to say it’s like this crossed with that to fit it into our neat categories of memory. If we really wanted to be accurate, we would call them mongoosecats or hyaenacats, or maybe even more accurately cat-like mongoose.
I haven’t done an animal cross game in a while, so when I ran across this animal, I thought it time to do another one. I was not familiar with this whiskery creature, but found it fascinating as soon as I saw it. I’m sure you will too, if you can figure out what it is. The animal is a living animal and as you can probably expect, a mammal. It is also on the endangered species list as a vulnerable species.
Put your guesses in the comments or join the conversation on Facebook and we’ll see if anyone can figure it out before I reveal the answer.